Calculator
Sock Cast-On Calculator
Tell us your foot circumference and your gauge — we'll give you the cuff cast-on count and the landmark stitch counts you'll hit at the heel and toe.
Calculator
How this works
Top-down socks cast on at the cuff and work down to the toe. The cast-on count needs to fit the leg snugly so the sock stays up — that's why socks use negative ease (a smaller stitch count than the foot circumference would suggest). The default 10% works for most yarns and feet. Drop to 5% for very firm yarn that won't stretch much, raise to 15% for very elastic yarn or feet that struggle to keep socks up.
Heel stitches are half the cast-on (the heel flap works on the back half of the sock). The toe-finish count is one-quarter of the cast-on, rounded to a multiple of 2 — that's the number you'll have when toe decreases finish and you're ready to graft the toe closed with Kitchener stitch.
Top-down only — for now
This calculator assumes top-down (cuff-down) construction. Toe-up socks start from a very small cast-on (typically Judy's Magic Cast-On, 16–24 stitches), then increase up to the foot circumference — that's a different math story that we'll add as a separate calc when demand warrants. If you knit toe-up, you can still use this calc to find your full foot-circumference stitch count, then plan your toe increases to reach that target.
Tips for measuring
- Measure with a flexible tape, not a ruler. Wrap around the widest part of the foot — across the ball, not the arch.
- Don't pull the tape tight. Snug but flat. Adult medium is typically 8–9 inches; ankle is usually slightly smaller than ball.
- Sock gauge is denser than typical knitting gauge. Use smaller needles than the yarn band suggests — usually US 0–3 (2–3.25 mm) for fingering-weight sock yarn.
- Always swatch sock fabric in the round if you knit in the round. Flat swatches lie about your real in-the-round gauge by a stitch or two.
- Once you've got your cast-on, the row-count calculator tells you how many rows of leg knit before starting the heel. A typical adult leg is 6–8 inches before the heel.